Home // International Journal On Advances in Internet Technology, volume 6, numbers 1 and 2, 2013 // View article

Dynamic Nearest Neighbors and Online Error Estimation for SMARTPOS

Authors:
Philipp Marcus
Moritz Kessel
Martin Werner

Keywords: 802.11 Fingerprinting, Orientation Filter, Mobile Phone Positioning, Location-Based Services

Abstract:
Location-based services are possibly the most popular services with respect to mobility, since they allow for the automated filtering of information relevant to the user. This paper presents a detailed evaluation of SMARTPOS, an indoor positioning system based on deterministic 802.11 fingerprinting and a digital compass. SMARTPOS is accurate enough to supply location estimates for indoor location-based services and can be deployed standalone on a mobile phone. Assuming that the mobile phone is held in front of the body, the system considers the user’s orientation to avoid errors caused by the blocking effect of the human body. For location estimation it employes a kNN approach on that part of the fingerprint database that corresponds to the user’s current orientation. As an extension to this approach, SMARTkNN is proposed which is based on dynamically selecting the number of nearest neighbors. This improved the mean position error to 1.10 meters and to a maximum position error of 2.65 meters in a 250 square meter environment in comparison to SMARTPOS which achieved a mean position error of 1.16 meters and a maximum position error of 2.74 meters. Furthermore, it is shown that the errors of SMARTPOS are normally distributed. Based on this fact, a novel online error estimator using bivariate Gaussians is proposed which gives the best approximation of the observed errors compared to existing methods. Additionally it was observed, that the density of the underlying radiomap strongly correlates to the maximum error and has a weaker impact on the observed mean error.

Pages: 1 to 11

Copyright: Copyright (c) to authors, 2013. Used with permission.

Publication date: June 30, 2013

Published in: journal

ISSN: 1942-2652